The reservoir will be filled in the winter under controlled conditions with surplus water from the Havant and Bedhampton Springs, as there is very little rain water available from the natural catchment to the north. As a compensation measure, a water flow will be maintained from the reservoir to the existing stream to the south. There will also be a carefully designed spillway to the existing stream to enable any storm water to be dealt with safely. Initial studies indicate that the reservoir will in fact reduce the risk of flooding downstream during storm events. In the case of an extreme event the new pipelines, used to fill the reservoir, can be utilised as an additional safety feature to drain water more quickly from the reservoir back to Langstone Harbour.

It is a requirement of the Reservoirs Act 1975 that the design of the reservoir is supervised by an independent engineer called the ‘Construction Engineer’, who is selected from a panel of engineers approved by the government. The Construction Engineer has already been appointed to approve the design of the reservoir embankments and associated structures, and he will also inspect the works during construction, if planning permission is granted. Filling of the reservoir can not be undertaken until the Construction Engineer has issued a certificate. Monitoring devices will be installed in the reservoir banks, and the embankments will be inspected by an independent engineer at regular intervals, as prescribed by the requirements of the Reservoir Act, which is regulated by the Environment Agency. This will include regular inspection and testing of the spillway and other draw down facilities.

Reservoir safety is an important issue and is strictly controlled by detailed legislation, i.e. the Reservoirs Act 1975. You can find more information on this at: